The functional vessels of human and animal bodies, such as blood vessels and ducts, occasionally weaken or even rupture. For example, in the aortic artery, the vascular wall can weaken or tear, resulting in dangerous conditions such as aneurysm and dissection. Treatment of such conditions can be performed by implanting a prosthesis within the vascular system using minimally invasive surgical procedures. An endoluminal prosthesis typically includes one or more stents affixed to graft material and is delivered to the treatment site by endovascular insertion utilizing introducers and catheters. Once the endoluminal prosthesis is radially enlarged, it should remain in place indefinitely by self-attachment to the vessel wall, acting as a substitute vessel for the flow of blood or other fluids.
Treatment of vascular conditions near a branch point with an endoluminal prosthesis is sometimes required. Typically, an endoluminal prosthesis for use near a bifurcation will have a main lumen body, for placement within the main aorta for example, and two branch lumens extending from the main lumen body into the branch arteries such as the iliac branch arteries. One such bifurcated prostheses is a single piece prosthesis. Such unitary structures have a main tubular body and pre-formed leg extensions. However, a more common alternative to the single piece approach is the use of a modular system. In these systems, one or both of the leg extensions can be provided separately and attached to a bifurcated distal end of the main tubular body to provide the final prosthesis. Examples of modular systems are described in PCT Patent Application Publication WO98/53761 and in U.S. Pat. No. 7,160,318, which are incorporated herein by reference. Known methods for attaching the main tubular body and the leg extensions includes, in one example, reliance on radial force and friction between the respective graft materials, which creates force for preventing the two parts from moving and/or pulling apart once they have been positioned and radially expanded in a desired location within the vasculature. In addition to such friction fit, the disclosed locking mechanism facilitates a secure seal and attachment between the bifurcated distal end of the main body stent graft and the proximal end of the leg extension(s), thus allowing the respective components to be locked together in a desired position within the vasculature.